An electronic module to be protected is connected between two power supply nodes and also, in some cases, to an input/output node intended to receive and deliver an input/output signal. For instance, when the module is in operation, one of the power supply nodes can be connected to a positive voltage and the other node can be connected to a negative or zero voltage (ground).
When the module is not operational, it may be subjected to an electrostatic discharge typically taking the form of a very brief current pulse (with a typical duration of several microseconds) between two of the nodes, with a maximum current of about 2 amperes, for example, and typically occurs after 10 nanoseconds. Typically, this corresponds, for example, to a pulsed potential difference applied between the two nodes through an equivalent RLC circuit, with a maximum voltage occurring after 10 nanoseconds and with an intensity of 1 to 4 kV HBM, for example 4 kV HBM for 2.5 amperes.
It should be noted at this point that the letters HBM are the abbreviation of the acronym “Human Body Model”, well-known to skilled practitioners in the field of electrostatic discharge protection, and signifying, notably, an electrical circuit intended to model an electrostatic discharge delivered by a human being and normally used for testing the sensitivity of devices to electrostatic discharges. This HBM circuit, which is the equivalent RLC circuit mentioned above, and to which a high voltage is applied, includes, notably, a 100 pF capacitor which is discharged through a 1.5 kohm resistance into the device to be tested. Thus, in the present case, an electrostatic discharge of 4 kilovolts HBM signifies that a potential difference of 4 kilovolts is applied to the HBM circuit.